Neuroscientists Discover the Roots of "Fear-Evoked Freezing"

When you feel scared, is your impulse to freeze in place, to take flight, or to fight? All three responses have a neurobiological foundation that is necessary for survival. Obviously, depending on the circumstance, there is a need for each three of these instinctive responses to a perceived threat.

Fight-or-flight has been studied in depth. Exciting new research from the UK is looking into the neurobiology of the "freeze" response. Before deciding to take flight or fight, most mammals freeze for a few milliseconds to assess the situation before making a next move.

Sometimes staying frozen in place is the best defense, sometimes it’s not... One problem with the freeze response in daily life is that it can cause people to become paralyzed by fear.

For the first time, neuroscientists at University of Bristol have identified a brain pathway that may be the root of the universal response to freeze in place when we are afraid. Their revolutionary study—released on April 23, 2014—discovered a chain of neural connections stemming from the cerebellum. When activated by a real or imagined threatening stimuli, these neural connections can cause the body to automatically freeze.

The new study titled “Neural Substrates Underlying Fear-Evoked Freezing: The Periaqueductal Grey—Cerebellar Link” was published in the Journal of Physiology. The Bristol researchers believe that understanding how these central neural pathways actually work will bring us closer to developing effective treatments for emotional disorders such as panic attacks, phobias, and general anxiety.

What Brain Regions Are Involved in Our Fear-Evoked Freezing Response?

The periaqueductal grey (PAG) is a brain region responsible for dictating how humans and animals respond to perceived danger. The PAG has long been known to receive various inputs about potential threats and trigger automatic reflexive responses that cause us to: freeze in place, give us the bloodflow to swiftly take flight, or the adrenaline rush to fight.

The University of Bristol neuroscientists have identified a specific brain pathway leading from the PAG to a highly localized part of the cerebellum called the pyramis which causes the body to automatically freeze in place.

The researchers discovered the pathway linking the PAG to the cerebellar cortex, which terminates as climbing fibers in lateral vermal lobule VIII (pyramis), in adult rats. If you’d like to read more about the cerebellum and climbing fibers check out my recent Psychology Today blog post “Neuroscientists Discover How Practice Makes Perfect.”

The central neural pathways involved in fear-evoked behavior are similar in most mammals. If neuroscientists can identify how these pathways work in animal studies, it could lead to the development of effective treatments for human emotional disorders.

Conclusion: Nothing to Fear but Fear Itself

Cerebellum in Red

These new discoveries on the neurobiology of fear responses are a first step toward better understanding the role that the cerebellum might be playing in the paralyzing power of anxiety, phobias, and fear in general.

As an athlete, I have always found it helpful to surf between a cerebral (or "top-down") approach to navigating fear responses that are coming from the "bottom-up" via the brainstem, cerebellum, and the subsequent fight-or-flight reaction of the sympathetic nervous system.

The new findings from research team at Bristol offer helpful insights for better understanding the root of paralyzing fear coming from deep inside the brain. Fear-evoked freezing is a universal response. Luckily, each of us can flex some cognitive muscle to override these innate neurobiological impulses.

Taking a few deep breaths in any fearful situation will stimulate the vagus nerve and the "rest-and-digest" aspects of the parasympathetic nervous system. This relaxation response unclamps the neurobiological grip of fear and allows us to "unfreeze" and move freely.

Although this research is in its earliest stages, the initial findings are promising. Dr. Stella Koutsikou, first author of the study, believes that identifying the actual neural circuitry linked to fear induced behavior is the key to developing more effective treatments for emotional disorders linked to a fear response.

In a press release, Bridget Lumb from University of Bristol concluded: "Our work introduces the novel concept that the cerebellum is a promising target for therapeutic strategies to manage dysregulation of emotional states such as panic disorders and phobias."

If you’d like to read more on this topic check out my Psychology Today blog posts: